Apm. Bay et al., THE INFLUENCE OF WATER ACTIVITY ON 3 GENOTYPES OF SNAP BEAN (PHASEOLUS-VULGARIS L) IN RELATION TO MECHANICAL DAMAGE RESISTANCE, Seed science and technology, 23(3), 1995, pp. 583-593
Mechanical damage has been identified as an important cause of vigour
loss and decreased seed quality and resistance to this damage in snap
bean (Phaseolus vulgaris L.) has been associated with seed coat colour
and moisture content. Two near-isogenic lines (white and dark-seeded)
selected for mechanical damage resistance (MDR) and a commercial cult
ivar (white seeded) of snap bean were studied by dropping seeds in a f
ree fall impact test from a height of 2.0 m. Resistance to compression
was also tested using a texture analyzer, TA.XT2. The dark seeded iso
genic line had a higher germination after impact than the white seeded
isogenic line followed by the commercial cultivar at each water activ
ity (a(w)) tested from 0.35 to 0.65 in 0.1 increments, Greater MDR to
impacts in the dark seeded line was attributed to higher lignin conten
t in the seed coats and better cotyledon to cotyledon attachment. The
germination results after compression showed that genotype differences
were observed only at 0.65 a(w), whereby the commercial cultivar rema
ined the most susceptible and the white-seeded isogenic line the least
susceptible. In conclusion, seed moisture content was the major gover
ning factor responsible for the degree of susceptibility to mechanical
damage while at each a(w) tested genotypic differences to impact dama
ge were measured.